October outside spending: $526 million

That’s the monster mountain of money outside political groups collectively spent in October to fill the nation’s airwaves, scorch your phone lines and flood your mailbox with flyers that directly promote or attack federal candidates, according to a POLITICO analysis of federal campaign spending disclosures.

Leading the way were the Karl Rove-backed super PAC American Crossroads, its nonprofit sister group Crossroads GPS and pro-Mitt Romney super PAC Restore Our Future, which has been fueled by tens of millions of dollars from billionaires such as casino mogul Sheldon Adelson and Texas home builder Bob Perry.

The three groups together spent nearly $173 million last month on ads and other communications, with the bulk targeting President Barack Obama. …